This invention relates to a waveform measuring and analyzing instrument for displaying a waveform signal and related numerical data with user operated means for analyzing said signal, storing the result of such analysis and visually presenting the result of the analysis.
Current scientific analysis of physical changes involves transducing the changes to electrical waveform signals and studying such waveform signals. Oscilloscope devices have been widely employed to visually present the waveforms for study and interpretation of the characteristics and changes.
Recent instrument development has provided for capturing the successive waveforms for analysis and comparison of the changes. Digital oscilloscopes, wherein an analog signal is digitized and stored in a digital memory unit are particularly useful. Individual points on such digitized waveforms can be displayed as digital values and the entire waveform can be reproduced as a digitized representation of the original analog waveform. The input waveform signal is sampled and digitized. Each digitized sample is placed in a separate time slot or location in the digital memory unit. The oscilloscope includes a display driver which is connected to read the memory unit. The display driver appropriately locates the beam on the screen for each location and increases the beam intensity at each location, and thereby reproduces a digitized representation of the waveform. The oscilloscope responds to a suitable trigger or timing signal to initiate acquisition of data. A hold mode control permits holding of a waveform for steady display. A triggered mode control may also be provided to capture and hold the portion of a waveform occurring immediately before a trigger control signal, or a portion of a waveform occurring a selected length of time after the trigger control signal. Successive portions of the waveform may be stored in a plurality of memory means for comparative analysis.
The prior art devices provide highly accurate means for measurement and recording of signal waveforms. Generally, the analysis of the waveform is by visual interpretation of the changes in combination with a manual calculation and reduction of the graphical information. In certain instances, specialized instruments include means for investigation of certain aspects or characteristics of the waveforms; for example, some pulse height analyzer instruments may include a specialized internal analyzing system. The analysis of the waveform, including appropriate reduction and mathematical calculations, otherwise requires the connection of the measuring instrument to separate specialized analyzing means or the recording of the data for subsequent analysis by data reduction and calculating apparatus. For example, digital recording oscilloscopes, transient recorders and the like may be connected to a computer which is programmed for particular processing the data. Specialized personnel familiar with programming and general operation of computers are required to program the computer as many scientists and engineers do not possess the specialized technical skills relating to programming machine language and the like. Further, specialized programming for each analysis can of course be relatively time consuming. Separate computing devices are also expensive and practically provided only by large laboratories and like institutions. Even then, time sharing requirement will normally not always permit adequately rapid access for analysis of the data.
The researcher also is often required to conduct the data acquisition sequence, with limited analysis provided by on-site devices and then transmit the acquired data for computer processing. There is not, therefore, a convenient method of complete on-site analysis of the waveforms. During investigation of changing event, various different investigations may, of course, present still many different possible approaches. Generally, with present measuring devices, each approach involves a reasonably extensive investigation with the usual laborious analysis of the results. A number of different approaches may be undertaken before the several results indicate the most productive detailed study to be undertaken.
Most instruments are constructed to record the incoming signal as an electrical voltage or current. The data is in corresponding electrical units and not directly in units for the particular parameter being measured. The conversions required further complicate on-site analysis.
There is therefore a substantial need for a measurement instrument which permits rapid, reliable capture and visual presentation, plus on-site analysis and reduction of repetitive or single event waveforms and which is sufficiently low cost and flexible for widely differing forms of waveform analysis. Further, the instrument should be readily employable by the scientist, engineer, technician and associated personnel without the necessity of having any detailed technical knowledge of the instrument's internal structure and by a relatively simple and readily understood procedure. The inventor has realized that the prior art approaches have been typically to develop special hardwired instruments. This approach appears to be based upon the designer's reaction to the fact that general analysis and development of different studies and investigation involve highly complex and widely different mathematical equations and procedures. However, the inventor has realized that in fact the reduction of most measured data can be executed with a small number of basic mathematical computational and logical procedures and that with the development of microprocessors, a generalized waveform measuring instrument can be provided for application in the analysis of transduced physical phenomena in which the waveform can be captured, manipulated and displayed for direct, improved on-site analysis. Further, the instrument can be constructed as a relatively inexpensive apparatus for convenient and reliable on-site analysis of complex and sophisticated waveforms with direct on-site data reduction.
In the art of graphic waveform display of monitored information, a selected point on the displayed waveform may be located by the use of a cursor which is a visible mark movable over the waveform to any particular point. The cursor may be in the form of a dot, pointer, cross hairs or the like and is manually positioned on the graph being displayed through a suitable input control. The position of the cursor may be monitored and the X-Y coordinates registered for readout to a suitable display terminal in the device. Except for specialized apparatus such as a pulse analyzer, a single cursor has generally been provided for visual display and positioning on the screen.
Although in the prior art, use of cursors provides assistance in analysis of a waveform, the inventor has recognized that, in fact, a very limited use of the capability of cursor positioning as an aid to total analysis of the graphical information has been made.
The inventor has further, therefore, found and provides a unique multiple cursor system which, in combination with the novel waveform measuring and analyzer instrument provides an extremely useful and practical tool for rapid and efficient analysis of waveforms.
The term waveform is employed herein to generically define any signal which can be captured and digitized for graphical display on a monitor oscilloscope or any other visual display means.